1. Field of the Invention
The present invention relates to a torque converting stator used with a transmission, particularly an automatic transmission in an automobile, an agricultural machine, a building machine, an industrial machine or the like and using a ratchet one-way clutch utilizing a ratchet (pawl) as a locking mechanism among one-way clutches having a back-stop function.
2. Related Background Art
In general, a one-way clutch used with an automatic transmission includes outer and inner races which are rotated relative to each other so that rotational torque is transmitted only in one direction by engaging sprags or rollers (for transmitting torque between the outer race and the inner race) with a cam surface provided on a track surface of the outer race or the inner race and the rotational torque is not transmitted in an opposite direction.
Among such one-way clutches, there is a ratchet one-way clutch in which a ratchet is used as a torque transmitting member for transmitting the torque between the outer race and the inner race. The ratchet one-way clutch is constituted by an outer face having pockets in its inner periphery, an inner race disposed in coaxial with the outer race and having notches in its outer periphery, pawls housed in the pockets and fitted in the notches of the inner race to achieve a locking condition of the one-way clutch thereby transmitting the torque between the inner race and the outer race, and elastic members for biasing the pawls toward the inner race.
In the ratchet one-way clutch having the above-mentioned arrangement, when the one-way clutch is rotated in one direction, since the pawls are freely slid on the outer periphery of the inner race, the outer race and the inner race are idly rotated relative to each other. Then, when the one-way clutch tries to be rotated in an opposite direction, the pawls are engaged by the notches, thereby establishing a lock-up condition of the one-way clutch.
As a conventional example in which the ratchet one-way clutch having the above-mentioned function is used as a torque converting stator, there is an arrangement as shown in FIG. 5.
FIG. 5 is an axial sectional view showing a conventional example of a torque converting stator using a ratchet one-way clutch. A stator 50 includes an outer race 53 disposed within an inner periphery of a vane wheel 51, and an inner race 54 disposed in coaxial with the outer race 53. At an inner periphery of the outer race 53, ratchets or pawls 55 are disposed within recessed formed in an outer periphery of the inner race 54.
Each pawl 55 is axially confined by the outer race 53 and an inner diameter portion 52 of the vane wheel 51. In general, the ratchet one-way clutch is slightly returned due to backlash when the pawls as torque transmitting members are engaged. Thus, impact or shock noise is generated upon engagement. In order to prevent generation of the impact noise, a damper spring 59 as a damper mechanism is provided between the ratchet one-way clutch mechanism and the vane wheel 51.
The above-mentioned damper mechanism must have certain damper capacity. To this end, a large damper spring must be used. Although a large space is required for receiving the large damper, since such a space is formed by providing a recess in a part of the outer race, there is a problem that strength of the outer race itself is reduced.
Therefore, an object of the present invention is to provide a stator in which desired damper capacity can be obtained without widening an installation position of a damper spring and making the damper spring larger.
To achieve the above object, a stator in which a damper mechanism is provided between a ratchet one-way clutch mechanism and a vane wheel, according to the present invention, is characterized in that the damper mechanism is provided with a friction element.
The damper mechanism is provided with the friction element in the stator in which the damper mechanism is provided between the ratchet one-way clutch mechanism and the vane wheel. Since the friction element compensates capacity of a damper spring of the damper mechanism, predetermined damper capacity can be obtained without widening a space for the damper spring and making the damper spring larger.
The friction plate is disposed between the vane wheel and an outer race of the ratchet one-way clutch mechanism. Thus, since the stator is subjected to fluid pressure in a torque converter to urge the outer race member and a stator wheel against each other, a friction surface of the friction plate is urged against an opposite friction surface with a moderate load, thereby obtaining the desired damper capacity more positively.
The friction plate has a support portion for supporting a side surface of the torque transmitting member of the ratchet one-way clutch mechanism. Thus, the pawl member as the torque transmitting member can conveniently be supported in an axial direction, thereby stabilizing an operation of the one-way clutch portion.